Electrophysiological studies will be performed on immature cortical neurons in the in vitro neocortical slice preparation, and on neurons dissociated from neocortical slices. The long term objectives of these experiments are to define the development of electrophysiological properties in immature neocortical neurons and to examine the mechanisms of epileptogenesis in the immature cortex. Specific aims include an examination of the sequence of development of subthreshold membrane properties and spike generation in immature neurons, and to examine the mechanisms of epileptogenesis in immature neocortical slices. Responses of immature slices to GABA antagonists and Ba++ will be examined at different developmental stages. Neurons will be identified directly in dissociated preparations or using intracellular HRP injections in slices. Standard current clamp techniques as well as patch clamp for whole cell recording and voltage clamp measurements will be employed. The results of these experiments will be relevant to general issues of normal and abnormal function in the immature cortex and will lead to a better understanding of the mechanisms underlying epilepsy in the immature brain.